Process for copolymerization of maleic anhydride with 1-olefins

ABSTRACT

MALEIC ANHYDRIDE AND POLYMERIZABLE LIQUID 1-OLEFINS HAVING FROM 4 TO 14 CARBON ATOMS ARE COPOLYMERS EMPLOYING A LIQUID-LIQUID DISPERSION AS THE REACTION MIXTURE BY USE OF EXCESS LIQUID 1-OLEFIN AS A DILUENT AND A MINOR AMOUNT OF A COPOLYMER OF MALEIC ANHYDRIDE WITH AN ALIPHATIC 1-OLEFIN HAVING FROM 14 TO 18 CARBON ATOMS AS A DISPERSING AGENT. MALEIC ANHYDRIDE AND A POLYMERIZATION INITIATOR BECOME DISPERSED IN THE MIXTURE OF OLEFIN AND DISPERSING AGENT AND POLYMERIZATION TAKES PLACE WHEN THE TEMPERATURE IS RAISED TO ABOUT 80*C. WITH AGITATION.

3,729,451 PROCESS FOR COPOLYMERIZATION OF MALEIC ANHYDRIDE WITHI-OLEFINS Ronald G. Blecke, Shawnee Mission, and Robert W. Hill,

Leawgod, Kans., assignors to Gulf Research & Development Company,Pittsburgh, Pa. No Drawing. Filed July 10, 1972, Ser. No. 270,331 Int.Cl. C08f N09 US. Cl. 260-78.5 R 3 Claims ABSTRACT OF THE DISCLOSUREMaleic anhydride and polymerizable liquid l-olefins having from 4 to 14carbon atoms are copolymerized employing a liquid-liquid dispersion asthe reaction mixture by use of excess liquid l-olefin as a diluent and aminor amount of a copolymer of maleic anhydride with an aliphaticl-olefin having from 14 to 18 carbon atoms as a dispersing agent. Maleicanhydride and a polymerization initiator become dispersed in the mixtureof olefin and dispersing agent and polymerization takes place when thetemperature is raised to about 80 C. with agitation.

DESCRIPTION OF THE INVENTION The preparation of copolymers of maleicanhydride with various unsaturated monomers, particularly ethylene andstyrene is well known in the art. More recently, copolymers of maleicanhydride with various branched and linear aliphatic l-olefins have beenprepared, some of which are finding uses in industry. It has been foundhowever, that in the preparation of a copolymer of maleic anhydride andsuch l-olefins that the recovery of the co polymers presents some fairlydifficult problems. The use of an excess of olefin in solutionpolymerization processes so as to obtain more complete reactionincreases the difficulty of separating the product.

A satisfactory practice which has been used as disclosed for example, inUS. Pat. 3,461,108, is to employ certain 'etficient solvents for thepolymerization step, keeping the monomers and in some instances thepolymers also in solution during the polymerization, and then adding tothe resulting solution another liquid, which causes precipitation of thepolymer products in finely divided filterable solid form. The selectionof the combination of reaction solvent and precipitating solvent iscritical. A very limited choice of solvent combinations exists, nocompletely satisfactory precipitating agent having been found for somecopolymers. Furthermore, the solvents are expensive and for this reasonmust be separated and recovered. The solvent separation, polymerfiltration and washing steps require bulky equipment and are timeconsuming.

It has been found in accordance with the present invention thatcopolymers of maleic anhydride with a variety of polymerizable l-olefinshaving from 4 to 14 carbon atoms can be produced in the form ofdispersions of solid particles in excess l-olefin as a diluent, providedthere is employed as dispersing agent an equimolecular copolymer ofmaleic anhydride with an aliphatic l-olefin having from 14 to 18 carbonatoms and the reaction mixture is heated to the vicinity of 80 C. withagitation to generate a liquid-liquid dispersion as a polymerizationreaction mixture.

Briefly, the present invention consists of a liquid dispersion processfor manufacturing a copolymer of maleic anhydride with an aliphaticl-olefin comprising the steps:

(a) forming a reaction mixture by mixing together at least onepolymerizable liquid l-olefin having from 4 to 14 carbon atoms, a minoramount of an equimolecular copolymer of maleic anhydride with analiphatic lolefin having from 14 to 18 carbon atoms as a dispers- UnitedStates Patent 3,729,451 Patented Apr. 24, 1973 "ice ing agent, apolymerization initiator and a quantity of maleic anhydride which isless than a molar equivalent of the amount of l-olefin present,

(b) agitating the reaction mixture of step (a) and heating to increasethe temperature to the point at which the reaction mixture becomes aliquid-liquid dispersion and the polymerization reaction is initiated,

(c) continuing agitation of the reaction mixture at a temperature nearthe decomposition temperature of the polymerization initiator until adispersion of solid copolymer particles in liquid l-olefin is obtainedas a polymerization product mixture, and

(d) recovering the solid particles of product from the polymerizationproduct mixture by filtration or vaporization of the liquid l-olefin.

The procedure outlined above eliminates the usual precipitation step insolution polymerization which requires costly separation of solvent andprecipitant when recycled, yields a liquid-liquid dispersion type ofreaction mixture which has a low viscosity and is easily stirred, pumpedand handled and permits operation at higher solids content in theproduct mixture. This results in greater throughput capacity and lowerprocess costs for equipment of a size comparable to that employed insolution polymerization. The dispersion copolymerization process of thisinvention is characterized by a combination of features which includethe use of a l-olefin comonomer as the dispersing medium, a uniquedispersing agent and a temperature program which allows the dispersionto develop. The process is discussed in greater detail below.

In carrying out the process there are some critical features which mustbe taken into account. One of the most critical features is selection ofthe polymeric dispersing agent. Only the copolymers of the maleicanhydride with the higher l-olefin appear to have good dispersionefficiency. Equimolecular copolymers of maleic anhydride with 14 to 18carbon l-olefins may be used for the purpose, preferably at aconcentration of 1 to 2 weight percent. The copolymers, which may bemade by published methods, for example the method of US. Pat. 3,560,456,are characterized in the following discussion.

The dispersing agents employed in the method of this invention arelinear, low molecular weight copolymers of straight chain l-olefins andmaleic anhydride. The olefin and maleic anhydride are present in a 1:1molar ratio, as shown in the following structural formula. R representsa linear alkyl substituent, the length of which is determined by thechoice of the olefin comonomer. In the tetradecene copolymer, forexample, the R substituent is dodecyl.

l-tetradecene copolymer l-octadecene copolymer Property Melting range, CEquivalent acid value Specific gravity Inherent viscosity 3 lTheoretical values, ignoring end group efiect. True density. a 5.0g./d1. in methyl isobutyl ketone at 77 F.

3 The copolymer dispersing agents are soluble in a wide variety oforganic solvents, as shown below. The solubility of these copolymers inhydrocarbon solvents is a unique characteristic, not shared bycopolymers of maleic anhydride with lower l-olefins.

SOLUBILITY OF OOPOLYMER DISPERSING AGENTS l-tetraloeta- NorE.-S=soluble;5 g./100 ml. SlS=slightly soluble; 1-5 g./100 ml.

In carrying on the heating program it is desirable to have the solidmaleic anhydride entirely mixed with liquid prior to raising thetemperature to the melting point of the maleic anhydride. Thetemperature should be increased slowly enough so that the mixing orstirring device employed in the reactor is able to maintain a conditionof efiicient mixing during the rise in temperature. If raising thetemperature to the decomposition temperature of the initiator is carriedout too quickly, without efiicient stirring, polymer may adhere to thewalls of the reactor. Although the process will operate and a polymerdispersion does form, the solid coating of polymer on the wall of thereactor will necessitate a cleaning operation. The speed with which thetemperature can be raised to the decomposition temperature of theinitiator depends to a great extent upon the efiiciency of the mixingapparatus in the reactor. This is largely a matter of choice from amongthe many types of mixing devices which are now available. A compromisewill have to be reached between mixing speed, power consumption,residence time in the reactor and various cost factors.

Selection of the polymerization initiator is made mainly on the basis ofthe decomposition temperature at which the compound produces freeradicals. This temperature should be above the melting point of maleicanhydride but below the softening temperature of the copolymer product.Peroxide initiators such as ditertbutyl peroxide and benzoyl peroxideand azobisisobutyronitrile are among those initiators which areavailable commercially.

Unlike the dispersing agents, the choice of polymerizable l-olefin isnot critical. Pure compounds or mixtures may be used in which there is apolymerizable vinyl group. The balance of the molecule may be straightchain, branched or cyclic in structure, including vinyl aromaticmonomers s h as styrene.

The polymer products obtained by the present process may be used for allthe purposes to which corresponding products have been used in the pastand have no observable deficiencies in chemical or physical properties.The solid particles of polymer obtained by this technique appear to havea very desirable physical structure, which render them easily handled inconventional processing equipment. The operation of the process isillustrated by the following specific examples.

Example 1 To 2.5 moles of l-hexene there is added 1.8 g. of tert.butylperoctoate as a polymerization initiator and 2.8 g. of anl-octadecene-maleic anhydride copolymer as a dispersing agent and 1 moleof solid maleic anhydride. The mixture is then heated with stirring. Asthe temperature rises above the melting point of the maleic anhydride (53 C.) the anhydride forms a second liquid phase underneath the liquidhexene. There is little tendency of the two liquid phases to intermix,even with vigorous agitation, until the temperature reaches the vicinityof C. and then only when the unique dispersing agent is present in themixture. When the two liquid phases begin to intermix and form aliquid-liquid dispersion there is evidence that the copolymerizationreaction has begun. With continued stirring for a sufficient time periodat a temperature of about 80 C. the polymerization procedure yields adispersion of solid copolymer particles in the excess liquid l-hexeneemployed as a diluent. When the polymerization reaction is judged to becomplete, the excess olefin employed as a liquid reaction diluent isseparated from the polymer by evaporation or filtration, yielding finelydivided non-tacky, solid copolymer.

Example 2 The procedure employed in this specific example is essentiallythe same as described in Example 1. The reaction vessel is charged with29.4 g. (0.3 mole) of maleic anhydride, 250 ml. of l-hexene, 2.0 g. ofbenzoyl peroxide, and 2 g. of maleic anhydride-l-octadecene copolymer.The temperature profile from 60 C. to C. requires one hour. Thedispersion develops normally and the reaction is allowed to proceed at90 C. for an additional 5 hours. A powdery white solid, M.P. 136140 C.,is isolated in 96% yield after filtration and drying. The copolymer hasa solution viscosity of 0.10 dl./ g.

Example 3 Example 4 The procedure and apparatus employed in this examplewere the same as described in Example 1. The reaction vessel was chargedwith 29.4 g. (0.3 mole) of maleic anhydride, 250 ml. of l-decene, 2.0ml. of tert.butyl peroctoate, and 2 g. of maleic anhydride-l-octadecenecopolymer. The temperature profile from 6090' C. was slower as thedispersion developed slowly. The resultant dispersion after filtrationgave a white granular solid, M.P. IDS-113 C.

Examples 5 and 6 Two batches of polymer were manufactured in a 50-gallon pilot plant reactor using the dispersion copolymerizationprocedure. The reaction charge for the two batches was:

l-hexene lbs 193 Maleic anhydride lbs 67 Tert.butyl peroctoate ..cc 520Maleic anhydride 1 octadecene copolymer dispersant lbs 2.3

Each batch was heated to 194 F. (90 C.), held two hours and cooled. Theexcess hexene was evaporated from the product using a Patterson-Kellyrotary vacuum dryer. Dried product was passed through a 4 inch screen.The

quantities of products of two batches and their properties are tabulatedbelow.

PILOT PLANT SYNTHESIS OF l-HEXENE COPOLYMER Example 5 6 Crude product,lbs

9 Reaction yield, percent L3 9 7 Dried product, lbs 113 Overall yield,percent 89 1 Inherent viscosity, dl./g 0 109 Volatiles, percent 0. 6

We claim:

1. A dispersion process for manufacturing a copolymer of maleicanhydride with an aliphatic l-olefin comprising the steps:

(a) forming a reaction mixture by mixing together at least onepolymerizable liquid l-olefin having from 4 to 14 carbon atoms, a minoramount of an equimolecular copolymer of maleic anhydride with a linearaliphatic l-olefin having from 14 to 18 carbon atoms as a dispersingagent, a polymerization initia tor and a quantity of maleic anhydridewhich is less than a molar equivalent of the amount of l-olefin present,

(b) agitating the reaction mixture of step (a) and heating to increasethe temperature to the point at which the polymerization reaction isinitiated,

(c) continuing agitation of the reaction mixture at a temperature nearthe decomposition temperature of the polymerization initiator until adispersion of solid copolymer particles in liquid l-olefin is obtainedas a polymerization product mixture, and

(d) recovering the solid particles of product from the polymerizationproduct mixture by filtration or evaporation of the liquid l-olefin.

2. A dispersion process for manufacturing a copolymer of maleicanhydride with l-hexene consisting essentially of the steps:

(a) forming a reaction mixture by mixing together 1- hexene, a minoramount, between 1 and 2 weight percent concentration, of anequimolecular copolymer of maleic anhydride with a linear aliphaticlolefin having from 14 to 18 carbon atoms as a dispersing agent, apolymerization initiator and a quantity of maleic anhydride which isless than a molar equivalent of the amount of l-hexene present,

(b) agitating the reaction mixture of step (a) and heating to increasethe temperature to the point at which the polymerization reaction isinitiated,

(c) continuing agitation of the reaction mixture at a temperature nearthe decomposition temperature of the polymerization initiator until adispersion of solid copolymer particles in liquid l-hexene is obtainedas a polymerization product mixture, and

(d) recovering the solid particles of product from the polymerizationproduct mixture by filtration or vaporization of the liquid l-hexene.

3. A dispersion process for manufacturing a copolymer of maleicanhydride with l-decene consisting essentially of the steps:

(a) forming a reaction mixture by mixing together 1- decene, a minoramount, between 1 and 2 weight percent concentration, of anequimolecular copolymer of maleic anhydride with a linear aliphaticl-olefin having from 14 to 18 carbon atoms as a dispersing agent, apolymerization initiator and a quantity of maleic anhydride which isless than a molar equivalent of the amount of l-decene present,

(b) agitating the reaction mixture of step (a) and heating to increasethe temperature to the point at which the polymerization reaction isinitiated,

(c) continuing agitation of the reaction mixture at a temperature nearthe decomposition temperature of the polymerization initiator until adispersion of solid copolymer particles in liquid l-decene is obtainedas a polymerization product mixture, and

(d) recovering the solid particles of product from the polymerizationproduct mixture by filtration or vaporization of the liquid l-decene.

References Cited UNITED STATES PATENTS 5/1966 Williams 106-309 8/ 1969Heilman et al 26078.5

1/1971 Field et a1. 260--78.5 2/1971 Hazen et a1. 260-785 I. KIGHT III,Assistant Examiner US. Cl. X.R.

